University of Maryland Extension

Harvest - Preserve

Harvesting

Fresh leaves may be picked as soon as the plant has enough foliage to maintain growth. Harvest up to three-quarters of the current season’s growth each time. Harvest herbs before they flower, otherwise leaf production will decline.

Pinch out stems at a leaf node to encourage lateral branching, instead of picking off a leaf here and there.

To ensure good oil content, pick leaves or seeds after dew has disappeared but before the sun becomes too hot. Pick seed heads as color changes from green to brown or gray. 

Preserving

Collect herbs for drying and storage just before flowering as this is when most herbs are at their peak of flavor. 

Wash herbs, with the leaves on the stems, lightly in cold running water to remove any soil, dust, insects or other foreign material. Drain thoroughly on absorbent towels or hang plants upside down to drain in a dry, airy location. Strip leaves off the stalks once plants have drained and dried. Remove all blossoms.

Natural or Air Drying

Drying is the traditional method of herb preservation. There are several methods of drying herbs. Which method you use depends on your time and space requirements. 

  • Tie fresh herb stems into small bundles and hang upside down in a dark, warm, airy place;
  • Spread herbs out on window screens to dry. Keep them out of the sun and turn them often;
  • Dry them with electric or solar dehydrators or use your oven. The pilot light in a gas oven or the oven viewing light in an electric oven provides a low, gentle heat. Do not use heat settings above 170°F;
  • Dry herbs in the microwave. Place the leaves on a paper plate or towel and microwave on low. Mix them every 30 seconds, watching to ensure that the herbs don’t “cook”;
  • Dry them in a frost-free refrigerator. The cold air circulates constantly. Heat is not used, so essential oils are not lost. Place the herbs in a paper lunch bag to dry and be sure all other foods are in well-sealed containers to prevent migration of odors; or
  • Use drying powders such as sand, borax, kitty litter, or silica gel; and
  • Store dried herbs in an air-tight bottle, preferably brown glass, in a cool place out of direct sunlight, and away from heat. Dried herbs lose flavor and potency after one year in storage.

Drying Seeds

Seeds take longer to dry than leaves – sometimes as much as 2 weeks for larger seeds. Place seed heads on cloth or paper. When partially dry, rub seeds gently between palms to remove dirt and hulls. Spread clean seed in thin layers on cloth or paper until thoroughly dry.

You can also dry herb seeds by hanging the whole plant upside down inside a paper bag. The bag will catch the seeds as they dry and fall from the pod.

Oven drying

For quick oven drying, take care to prevent loss of flavor, oils, and color. Place leaves or seeds on a cookie sheet or shallow pan not more than 1 inch deep in an open oven at low heat – less than 180° F for about 2 to 4 hours.

Microwave ovens can be used to dry leaves quickly. Place the clean leaves on a paper plate or paper towel. Place the herbs in the oven for 1 to 3 minutes, stirring every 30 seconds.

Freezing Herbs

Freezing is a quick and easy method to preserve herbs and is the best way to conserve the essential oils, phytochemicals, and vitamins. There are two basic methods:

Using the first method, you rinse the herbs quickly in cold water, shake off the excess and chop coarsely. You can freeze them in cubes by placing generous pinches of herb in ice cube trays, then cover with water to prevent freezer burn. Later, transfer frozen cubes into a freezer bag.

For the second method, loosely spread the herbs onto a cookie sheet to freeze. Then transfer them into a large plastic bag and seal. In both cases, when they thaw, the herbs will be limp and possibly discolored. They will be unsuitable for garnish, but they’ll taste and smell nearly as fresh as the day you picked them.

Storage

When completely dry, the leaves may be screened to a powder or stored whole in airtight containers, such as canning jars, with tightly sealed leaves.

Seeds should be stored whole and ground as needed. Leaves retain their oil and flavor if stored whole and crushed just before use.

For a few days, it is very important to examine daily the jars in which you have stored dried herbs. If you see any moisture in the jars, remove the herbs and repeat the drying process. Herbs will mold quickly in closed jars if not completely dry.

Once you are sure the herbs are completely dry, place them in the airtight containers, and store in a cool, dry place away from light. Never use paper or cardboard containers for storage as they will absorb the herbs’ aromatic oil.

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